venules and veins differ in size structure and function Kelsee Aimee How it works Blood leaves heart through pulmonary trunk and aorta Vessels branch forming major arteries that carry blood to body organs ID: 591157
Download Presentation The PPT/PDF document "13-1 Arteries, arterioles, capillaries," is the property of its rightful owner. Permission is granted to download and print the materials on this web site for personal, non-commercial use only, and to display it on your personal computer provided you do not modify the materials and that you retain all copyright notices contained in the materials. By downloading content from our website, you accept the terms of this agreement.
Slide1
13-1 Arteries, arterioles, capillaries, venules, and veins differ in size, structure, and function
Kelsee
, Aimee Slide2
How it worksBlood leaves heart through pulmonary trunk and aorta
Vessels branch forming major arteries that carry blood to body organs
More branching within organs forms arterioles
Arterioles provide blood to over 10 billion capillaries
Vital functions of the cardiovascular system occur within the capillaries
Blood flowing out of capillary network enters
venules
(slender vessels that form veins) Slide3
Structure of vessel walls
The walls of arteries and veins contain three distinct layers:
Tunica intima-
the innermost layer of a blood vessel, includes the endothelial lining of the
v
essel and an underlying layer of connective tissue dominated by elastic fibers
Tunica media-
the middle layer, contains smooth muscle tissue in the framework of collagen and elastic fibers. When these smooth muscles contract, vessel diameter decreases; when they relax vessel diameter increases
Tunica externa-
outer layer that forms a sheath of connective tissue around the vessel. Its collagen fibers may intertwine with those of adjacent tissues, stabilizing and anchoring the blood vessel. Slide4Slide5
ArteriesBlood passes through elastic arteries, muscular arteries, and arterioles
Elastic arteries:
large resilient vessels
Ex. Pulmonary trunk and aorta and major arterial branches
Muscular arteries:
medium sized/distribution arteries, distribute blood to skeletal muscles and internal organs
Ex. External carotid arteries of the neck
Arterioles:
much smaller than muscular arteries Slide6
Elastic ArteriesWalls are dominated by elastic fibers
Absorb pressure changes that occur during cardiac cycle
During ventricular systole (blood pressure rises quickly) elastic arteries are stretched, diameter increases
During ventricular diastole, (blood pressure declines) the elastic fibers go back to normalSlide7
Muscular Arteries and ArteriolesMuscular arteries contain more smooth muscle cells than elastic fibers
Tunica media of an arteriole contains two layers of smooth muscle cells
These muscle layers change the diameter, which alters blood pressure Slide8
CapillariesSingle layer of endothelial in basement membrane
No tunica externa or tunica media
Function in a network called capillary bed
The only blood vessels whose walls permit exchange between blood and surrounding interstitial fluid
Walls are thin and diffusion distances are short
Diameter is small, causing the blood flow to be slow which gives adequate time for diffusion
Each capillary is protected by a precapillary sphincterSlide9Slide10
The processA single arteriole feeds dozens of capillaries which connect to several
venules
Blood usually flows from arterioles to
venules
at a constant rate however it is variable
Vasomotion
Smooth muscle fibers respond to local changes in interstitial fluid
AutoregulationSlide11
The process cont. Alternate routes for blood flow are formed by anastomosis outlet
The joining of blood vessels
Circumstances can cause blood to completely bypass a capillary bed through an arteriovenous anastomosis
vessel that connects an arteriole to
venule
A single capillary bed can be supplied by an arterial anastomosis
More than one artery fuses and gives rise to arterioles
If one or more artery is blocked the others can
still deliver
blood and tissue will not be damaged Slide12
VeinsCollect blood from tissues and organs and deliver it back to heart
Venules
- the smallest
Medium sized veins- similar to size of muscular arteries
Contain valves to prevent backflow of blood
Large veins- include two vena
cavae
and tributaries in abdominopelvic and thoracic cavities
Thin walls due to lower pressure
Pressure is so low it cannot overcome the force of gravitySlide13Slide14